The optical disks are becoming more and more important for backing up data and exchanging information because the optical disks have many advantages including a high storage capacity, easy to handle and carry, and a long preserving time for the stored data. Thus, among all the data storage solutions, the optical disk drives can be found all around us such as in desktop computers, laptop computers, DVD players, and even some instruments or electronic products.
Referring to FIGS. 1A and 1B, perspective and exploded views of a conventional disk drive 2 are shown to include an outer casing (not visible since removed), a disk tray 10 disposed within the casing for receiving an optical disk 4 thereon and having a reading opening 1002 formed therethrough, a clamp-holding seat 12 disposed above the disk tray 10 and having a clamp opening 1202, a clamp 6 disposed within the clamp opening 1202 in the clamp-holding seat 12 and projecting downwardly from a bottom side of the clamp-holding seat 12, and a spindle motor 8 disposed below the disk tray 10.
Referring to FIGS. 2A and 2B, perspective and side views of the conventional disk drive 2 are shown and the latter includes a gear system 1402, a driving motor 14 for driving the disk tray 10 via the gear system (1402+1602) between an extended position, in which, the disk tray 10 extends outwardly from the casing (not shown) and a retracted position, in which, the disk tray 10 retracts inwardly into the casing (not shown). The conventional disk drive further includes a spindle-carrier frame 18 that is disposed below the disk tray 10 for carrying the spindle motor 8 thereon and that has an inner end portion 1802 pivoted to the casing and an outer end portion 1804 formed with left and right inclined guiding slots 1806, and a lifting plate 16 that is disposed within the casing adjacent to the spindle-carrier frame 18, that extends in a transverse direction relative to a longitudinal axis of the casing, and that has left and right couplers 1604 engaging slidably the slot-confining walls of the guiding slots 1806 in the spindle-carrier frame 18. The lifting plate 16 is operably connected to the driving motor 14 via the gear system (1402+1602) and is movable along the transverse direction to left and right sides of the casing upon rotation of the driving motor 14 such that rotation of the latter in the clockwise direction results in movement of the lifting plate 16 to one of the left and right sides of the casing, which, in turn, lifts the spindle-carrier frame 18 via the reading opening 1002 in the disk tray 10 to an upper position (i.e. reading position), where the spindle motor 8 cooperates with the clamp 6 to sandwich the disk 4 therebetween, and that rotation of the driving motor 14 in the anti-clockwise direction results in movement of the lifting plate 16 to the other one of the left and right sides of the casing, which, in turn, lowers the spindle-carrier motor 8 to a lower position (non-reading position).
Referring to FIGS. 1 and 3, the spindle motor 8 is mounted on the spindle-carrier frame 18 via a bearing unit 20 (see FIG. 1B) for rotating the disk 4 when the spindle-carrier frame 18 is disposed at the reading position. The spindle motor 8 has a top covering 804 provided with a magnetic element 802 that attracts the clamp 6 so as to sandwich the disk 4 between the clamp 6 and the top covering when the spindle-carrier frame 18 is disposed at the reading position. However, during movement of the spindle-carrier frame 18 to the lower position, the spindle motor 8 generally collides against the bearing unit 20 due to a sudden release of the spindle motor 8 from the clamp 6, thereby producing an undesired noise and consequently shortening the service life of the conventional disk drive 2.
FIG. 3 represents the current flow with respect to a time period during disengagement of the spindle motor 8 from the clamp 6. Note that to disengage the spindle motor 8 from the clamp 6, an electrical current of amount B is supplied to the driving motor 14 to overcome the magnetic attraction between the clamp 6 and the magnetic element 804. In order to ensure proper disengagement of the top covering 804 from the clamp 6, the electrical current B should be greater than an initial current A. After the lowering operation of the spindle-carrier frame 18 to the lower position, the electrical current B is gradually reduced to C and D respectively, wherein the electrical current D is the amount for driving the disk tray 10 to the retracted position. Generally D is smaller than A.